Greetings, Sue, and welcome to the Airforums!
Leaks in vintage rigs are sometimes pretty elusive. We've been battling with seals on our 67 for years, primarily sealing around the lower windows in the front, where the leaks seemed to be coming from. But this last time I took Inland Andy's advice to seal around the hinges at the top of the windows (where it didn't appear to be leaking anyway). And, suddenly, the last rain yielded a very distinctly different pattern of leaking. Methinks I may be on the right track this time!
But your Airstream has different windows from those of a couple of years later, and leaks can come from almost bizarre locations, including all the way on the roof (water then seeping down inside the wall to wind up at the windows).
Main message: Don't necessarily buy into the idea that a leak apparent at a window is a leak at the window.
Oh, and because you'll probably hear it anyway from multiple sources here, get rid of that silicone for most uses on Airstreams! There's a whole lot better stuff available. Check out, among other sources, VintageTrailerSupply
as well as Inland